Polycarbonates are useful in the manufacture of articles and components for a wide range of applications, from automotive parts to electronic appliances. Because of their broad use, it is beneficial to provide polycarbonate compositions with very good flame retardance. It is further beneficial, particularly in building and transportation applications, to provide polycarbonate compositions that produce very low smoke when ignited, with low toxicity.
While numerous flame retardant and/or low smoke polycarbonate compositions are known, there remains a need in the art for compositions that meet the most stringent of the flame retardance and low smoke standards. One difficulty in meeting these standards is that use of one component to improve flame retardance can concomitantly degrade another selected property, such as smoke density. It is particularly difficult to meet these standards while also maintaining good mechanical properties. Among the more stringent standards is the French NF F 16-101 (October 1988). It is very difficult for thicker (greater than 2 mm) thermoplastic materials to achieve an M1/F1 rating in accordance with this standard. In order to obtain M1/F1 rating, a sample must pass three different tests: the “drip test” determined in accordance with NF P 92-505; the “epiradiateur” test determined in accordance with NF P 92-501, and the “F test,” consisting of the smoke density test determined in accordance with NF X 10-702 and the smoke toxicity test determined in accordance with NF X 70-100. It is particularly difficult to obtain an M1/F1 rating for the same composition at a range of thicknesses, as thinner sheets can more readily pass the flammability tests, but not the smoke density tests, and vice versa.
Particularly for polycarbonate compositions, dripping is a major cause for failing the M1 rating. Polytetrafluoroethylene (PTFE), which is used to prevent dripping in Underwriter Laboratories (UL) tests, does not prevent drip dripping in the tests conducted in accordance with NF P 92-505. Addition of mineral fillers such as TiO2, talc, or clay to polycarbonate compositions can be effective to prevent drip in the UL tests. However, the effect is apparent only at lower levels of filler (less than 15 weight percent (wt. %)). Further, clay is often found to be more effective than talc in UL tests.
There accordingly remains a need in the art for polycarbonate compositions that meet stringent standards for flame retardance, in particular reduced dripping in accordance with NF P 92-505. There also remains a need in the art for polycarbonate compositions that meet stringent standards for flame retardance, reduced smoke density, and, beneficially, reduced toxicity. It would still further be an advantage if the polycarbonate compositions could be formulated without having a detrimental effect on mechanical properties.